1. Field of the Invention
The invention is in the general field of improved methods of preparing polyvinyl-halide containing polymers (e.g. polyvinyl chloride).
2. General Background
The preparation of vinyl halide-containing polymers by suspension polymerization of vinyl halide either alone or in combination with other monomers is well-known. Briefly, the process comprises adding water, the monomer, initiator and suspending agent to the reaction vessel which is jacketed. The reaction mass is heated by injecting steam into the reaction vessel. Once at desired temperature the reaction is maintained at a predetermined temperature by controlling the temperature of the water in the jacket. The reaction is allowed to proceed until it reaches a predetermined conversion level. The reaction may be terminated by the addition of a free radical inhibitor (also known as a chain stopping agent). Usually, at the same time the reaction vessel pressure is reduced by venting usually to a compressor.
Alpha-methyl styrene (AMS) has been used for many years in the commercial production of polyvinyl chloride. Prior to the advent of steam stripping of the slurry to remove unreacted monomers, AMS was considered an effective terminating agent. However, at the higher temperature encountered with steam stripping AMS is not entirely satisfactory as a terminating agent. Presumably, the terminating reaction is reversible or some other adverse reaction is taking place. Accordingly, it would be desirable to have another material which is effective as a terminating agent.
Our invention is directed to a method of terminating polymerization of vinyl halide-containing polymers by the use of a material obtained by the alkylation of p-methoxyphenol with nonene. This material also functions an antioxidant in the product.